I/Q multiplexed code assignment for fast cell search under hierarchical cell structure

For wireless multimedia services in cellular systems, it is desirable to asynchronously operate the cell sites because of flexible system deployment form outdoors to indoors. For this, we should be able to minimize the cell search time which is much longer than in case of synchronous operation. A novel I/Q multiplexed code assignment is proposed for asynchronous cell site operation under hierarchical cell structure, in which the I-channel code as a group code and the Q-channel code as a cell-specific code are assigned to a forward pilot channel. As a decision algorithm, a SPRT (sequential probability ratio test) is used to further reduce the acquisition time of the I/Q multiplexed code. Simulation results show that cell search from macro to micro, or vice versa, can be accomplished in less than about 50 ms at 90% of the locations